Partners
United States
Environmental Protection
Agency
The technical organizations that contributed to the
development of the hydraulic hybrid yard
hostler are: U.S. EPA, ARM Terminals, Parker-
Hannifin, Kalmar Industries, FEV, Inc., R. H. Sheppard
Co., Inc., and Webasto.
APM TERMINALS
Parker
Ceries
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nnn HYDRAULIC HYBRID VEHICLES
HIGHEST EFFICIENCY - LOWEST COST
Using innovative series hydraulic hybrid technology,
EPA and its industry partners have created a highly
efficient and cost-effective hybrid. This system is
projected to improve the stop-and-go fuel efficiency
of off-road container tractors known as yard hostlers
by 50-60 percent and reduce climate change C02
greenhouse gas emissions by over 30 percent. The
unique energy recovery technology used to stop a
hydraulic hybrid vehicle also reduces brake wear by
up to 75 percent, increasing the net operating sav-
ings substantially.
Each high efficiency yard hostler could
save a terminal operator over 1,000
gallons of fuel per year.
Even more remarkable, when manufactured in high
volume there is the potential to recoup the hybridi-
zation costs from fuel and maintenance savings in
three to five years.
The lifetime fuel savings for this
vehicle's typical 12 year lifespan could
be over $35,000 (assuming fuel costs of
$3/gallon).
HOW IT WORKS
This innovative technology is simple. The main compo-
nents in a full series hydraulic hybrid vehicle are:
• High pressure accumulator — stores energy by
using hydraulic fluid to compress nitrogen gas much as
a battery is used to store energy in a hybrid electric
vehicle.
• Rear drive pump/motor (acting as a motor) —
converts pressurized hydraulic fluid into rotating power
for the wheels.
• Low pressure reservoir —holds the spent fluid after
it has been used by the rear drive pump/motor.
• Rear drive pump/motor (acting as a pump) —
captures braking energy by pumping hydraulic fluid
back into the high pressure accumulator.
• Engine pump/motor (acting as a pump) — creates
additional high pressure fluid needed to drive the vehi-
cle, storing any excess in the high pressure accumulator.
• Hybrid controller — monitors the driver's accelera-
tion and braking, and sends operating commands to
the various hybrid system components.
A typical yard hostler vehicle used to move containers at a sea port terminal.
Hydraulic hybrid vehicles rely on proven tech-
nology which is being evaluated in package
delivery vehicles, shuttle buses, and refuse
trucks.
High Pressure
Accumulator
\ (Vertically
Mounted)
The three key design features that contribute to im-
proving the fuel efficiency of hydraulic hybrid vehicles
3:
Regenerative Braking — To slow or stop the
vehicle, the rotating energy of the wheels is used to
pump fluid from the low pressure reservoir into the
high pressure accumulator. This stored energy is
then used to accelerate the vehicle. Up to 70 per-
cent of the energy normally wasted during braking
is recovered and reused.
2. Engine Shutoff (Me reduction) — Over 40 per-
cent of a yard hostler's working hours are spent
waiting at the port with the engine idling. The vehi-
cle's engine-off power steering and heating systems
allow the engine to be shut off during these waiting
periods. The unique series hybrid design also en-
ables the engine to be automatically turned off
when it is not needed, such as during braking.
These features reduce vehicle emissions, as well as
operating and maintenance costs.
3. Optimum Engine Control — In the full series
hybrid design, there is no conventional transmission
and driveshaft to connect the engine dirctly to the
wheels. This frees the engine to be operated at its
best efficiency "sweet" spot, achieving optimum
vehicle fuel economy.
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